This invention concerns a polyarylene thioether (hereinafter referred to as PATE) composition excellent in processability and toughness in which crystallizing rate is increased and the size of the spherulites is reduced.
PATE has been developed as a heat resistant, chemical resistant and flame resistant thermoplastic resin. Particularly, since PATE crystallizes easily, it has advantageous features in that it is excellent in the melt processability such as for injection molding and in that resultant molding products have excellent physical properties such as dimensional stability, strength, hardness and insulating performance. Taking these advantages, PATE has been employed in the industrial fields of electric, electronics, automobiles, aircrafts, precision instruments and chemicals.
However, those PATEs having high crystallizing rate from the molten state and thus suitable for injection molding, etc. generally show a tendency of producing coarse spherulites upon crystallization and, as a result, their molded products become poor in toughness and impact resistance. While on the other hand, those PATEs comprising fine spherulites formed upon crystallization from the molten state and providing molded products of high thoughness and impact resistance, generally show lower crystallizing rate and, accordingly, not suitable for the melt procesing, such as injection molding, which requires short molding cycle.
In view of the above, the conventional PATEs involve a problem for obtaining molded products of high toughness and high impact resistance by means of injection molding, etc.
The present inventors have made an extensive study on a method of improving the crystallizing rate together with toughness and impact resistance of PATE resin and, finally, have found that an adequate blend of a PATE having extremely high crystallizing rate (hereinafter referred to as PATE of high crystallizing rate) and a PATE forming extremely fine spherulites (hereinafter referred to as fine spherulitic PATE) has surprisingly higher crystallizing rate and forms smaller size of spherulites as compared with PATEs of identical solution viscosity or melt viscosity used alone (PATE just obtained from polymerization reaction). It is supposed that this phenomenon is due to the fact that at first, the fine spherulitic PATE forms a great number of crystal nuclei in the cooling step of the molten blended composition and then the PATE of high crystallizing rate grows rapidly into spherulites around the nuclei.
Further, it has surprisingly been found that the crystallizing rate of the blend, depending on the composition of the blend, can be higher than that of the PATE of high crystallizing rate alone which is one of the components thereof.
The present invention has been accomplished based on the above findings.